• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권4호
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• pp.178-184
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• 2005

In this paper, using diplexer structure and varactor diode controlled by reverse bias voltage for diplexer switch gives possibilities to improve isolation and current characteristics. 1 have newly designed switch with high isolation by application varactor diode corresponding to capacitor of diplexer. The low-pass filter for proposed tunable diplexer passes the microwave signal in the bandwidth for wireless cellular network systems and high-pass filter passes it in the bandwidth for wireless personal communication services (PCS) network systems. As the capacitance of the low-pass filter increases, the cut-off frequency can be moved to low frequency, so that the switch is on state in cellular bandwidth and off state in the PCS bandwidth, in contrast to, as the capacitance for attenuation characteristic of high-pass filter increases, it can be moved to high frequency, so that the switch is off state and on state in the cellular bandwidth. it is possible to improve isolation and current consumption characteristics by application diplexer design methods and varactor diode. 1 expect that the tunable diplexer circuit and design methods should be able to find applications on MMIC and low temperature copired ceramic (LTCC).

• Journal of information and communication convergence engineering
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• 제7권2호
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• pp.98-106
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• 2009

Process Control Systems (PCSs) or Supervisory Control and Data Acquisition (SCADA) systems have recently been added to the already wide collection of wireless sensor networks applications. The PCS/SCADA environment is somewhat more amenable to the use of heavy cryptographic mechanisms such as public key cryptography than other sensor application environments. The sensor nodes in the environment, however, are still open to devastating attacks such as node capture, which makes designing a secure key management challenging. In this paper, a key management scheme is proposed to defeat node capture attack by offering both forward and backward secrecies. Our scheme overcomes the pitfalls which Nilsson et al.'s scheme suffers from, and is not more expensive than their scheme.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.257-260
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• 1997

Bluetooth is the most promising network paradigm which ca open the new area in the information technology. Especially, bluetooth can link all the electrical products and PCs(Personal Computer) to cellular phone or PDA. In this paper, the data from ECU which are gathered by scanner are communicated between tow PCs using the bluethooth modules. The acquired data are ECU's self diagnosis signal and sensor output signal. Self diagnosis signals are very important to check the ECU's state and sensor output signals. Using these data, the possibility of wireless communication with ECU is developed and verified. Protocol stack of bluetooth is L2CAP through HCI and wireless communication software of ECU's signal is developed using VC++ in Windows 98 environment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2747-2749
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• 2000

The KEPRI has been developing the medium/small scale Distribution Automation System(DAS) that adopts wireless transmission media for exchanging information between master and remote terminals. It was concluded that Short Message Service(SMS) of Personal Communication Service(PCS) was the best wireless transmission media for the medium/small scale DAS in the last year. However. we had problem that PCS had long transmission delay. Therefore. SMS phones will be substituted with Radio Link Protocol(RLP) modems having transmission delay less than 5 seconds. This paper describes wireless networks for DAS, practical experience.

• 한국컴퓨터정보학회논문지
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• 제22권5호
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• pp.29-39
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• 2017

In this paper, we analyse security threats and security requirements about the designated PC solution which restricts usable PCs that are only an user own PCs or a registered PC for online banking or very important services. Accordingly, causable threats of the designated PC solution are classified a process, a network layer, a software module, and an environment of platform, and we draw security requirements based on analysed security threats. Results of this research are considered utilization of criteria for improving security of the designated PC solution and standards for giving hint of imposition of the designated PC solution.

• 전기전자학회논문지
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• 제15권4호
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• pp.339-344
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• 2011

In this paper, we proposed an internal multi-band monopole antenna for mobile phone that can be used for smart phones. The proposed antenna has a small volume of $38{\times}8.5{\times}5\;mm^3$, ground size is $100{\times}60\;mm^2$, and covers the GSM900 (Global System for Mobile communications : 880-960 MHz), DCS (Digital Communications System : 1710-1880 MHz), K-PCS (Korea-Personal Communications Service : 1750-1870 MHz), US-PCS (US Personal Communications Service : 1850-1990 MHz), Bluetooth (2400-2483 MHz), Wibro (2300-2390 MHz) and WLAN (Wireless Local Area Network : 2400-2483.5 MHz) bands. The measured peak gains of the implemented antenna are 1.15 dBi at 920 MHz, 3.58 dBi at 1795 MHz, 3.46 dBi at 1810 MHz, 2.91 dBi at 1920 MHz, 5.18 dBi at 2345 MHz, 3.37 dBi at 2442 MHz.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.303-305
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• 2002

SSTF(Samsung Superconducting Test Facility) has been constructed at Samsung Advanced Institute of Technology to test the KSTAR(Korea Superconducting Tokamak Advanced Research) superconducting magnets and conductors. The SSTF DAC(Data Acquisition and Control) system basically consists of VME I/O modules, host PCs, and Ethernet links. VxWorks is used for the real-time OS of the VME IOC(Input/output Controller). EPICS (Experimental Physics and Industrial Control System) provides a software architecture for the communication between IOCs and host PCs. For the efficient management of measured data, the database management programs through NFS(Network File System) have been developed and successfully operated. In this paper, the current status of the SSTF DAC system, DBMS(DataBase Management System), recent test results, and future plans are presented.

• 정보처리학회논문지C
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• 제10C권1호
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• pp.111-118
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• 2003

정보화 시대가 도래하면서 통신망의 장애에 의한 서비스 단절은 사회 각 분야에 치명적인 영향을 끼치게 된다. 통신망 장애에 의한 피해를 계량적으로 평가할 때 서비스를 이용하는 가입자 측면에서 살펴보면 얼마나 많은 장비가 장애에 의해 피해를 입었는가 하는 것보다는 얼마나 많은 가입자가 얼마나 오랫동안 서비스를 이용하지 못하였는지가 더 중요할 것이다. 따라서, 본 논문에서는 국내 무선통신망의 장애발생시 가입자에 대한 충격정도를 정량적으로 산출하여 장애영향을 평가할 수 있는 장애영향 평가 모델에 대하여 제안하였다. 이때, 국내 무선통신망 환경에 적합한 장애영향 평가 모델을 제안하기 위하여 국내 무선통신망의 가입자수, 무선서비스 유형별 중요도에 따른 가중치를 고려하였고 장애에 의해 영향 받은 가입자수를 계량화하는 크기 비중 값 계산식을 개발, 적용하였다. 장애영향 평가 모델의 적용결과를 살펴보면 PCS 네트워크에서 30,000명의 가입자가 30분 동안 "Mobile to Land" 서비스를 제공받지 못했을 경우 장애지수는 2.5로서 10,000명의 가입자가 서비스를 제공받지 못한 경우의 0.5 보다 5배 정도 가입자에게 충격을 주는 것으로 나타났으며, 30,000명의 가입자가 30분 동안 "Mobile to Land" 및 "Local Mobile to Mobile"의 서비스를 동시에 제공받지 못했을 경우는 3.75 이었다.비스를 동시에 제공받지 못했을 경우는 3.75 이었다.

• 전자공학회논문지S
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• 제34S권2호
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• pp.11-20
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• 1997

It is a recent trend that mobile communications and PCS are intergrated into the broadband network. Broadband mutlimedia traffic will be transported over the integrated network. In this paper, we propose a connection re-routing method for fast inter-switch hadoffs and dynamic resurce reservation scheme, which is based on the proposed re-routing method, for the ATM-based personal communications network. To reduce the delay for re-routing method, for the ATM-based personal communications network. To reduce the delay for re-routing, the proposed re-routing method is to reserve VPI/VCIs for possible inter-swich handoff calls in advance. Our reservation scheme is to statistically reserve the fixed resources for possible inter-switch handoff calls, according to the QoS of the handoff calls. The simmulation reslts show that our proposed scheme satisfies the required QoS of handoff calls and keep the dropping probability of handoff calls lower than other schemes.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.1129-1132
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• 1999

This paper deals with the design and implementation of an Ethernet-based communication protocol to be used in PC-based I/O interface systems. Recently, the performance of PC systems is being highly improved and Ethernet is used as the stable communication network over the world. We develop a new protocol driver with the capability of accessing Ethernet directly using NDIS(Network Driver Interface Specification), the network interface standard of Windows O.S. in PC, and install it at the application layer of the protocol structure. Its major roles are the supplement of CSMA/CD algorithm, the effective use of the long data frame of Ethernet, and the real-time transmission of data frames. This paper represents the possibility of the real-time control network and systems based on PCs and Ethernet.